Demonstration model of a hot air motor and pump



H. SCHULZE Dec. 2, 1969 3,481,142 DEMONSTRATION MODEL OF A HOT AIR MOTOR AND PUMP 2 Sheets-Sheet 1 Filed March 18, 1968 INVENTOR Harald Schulze BY ATTORNEYS.

H. SCHULZE 3,481,142

DEMONSTRATION MODEL OF A HOT AIR MOTOR AND PUMP Dec. 2 1969 2 Sheets-Sheet 2 Filed March 18, 1968 INVENTOR. Harold Schulze ATTORN EYS.

United States Patent 3,481,142 DEMONSTRATION MODEL OF A HOT AIR MOTOR AND PUMP Bochum, Germany, assignor to Leybold- Harald Schulze,

G.m.b.H., Cologne-Bayental,

US. Cl. 60-24 8 Claims ABSTRACT OF THE DISCLOSURE To demonstrate the fundamental principles of hot air motors and pumps, a working piston and a displacer piston are slidably mounted within a transparent coolable cylinder. The displacer piston includes a displacer piston head, oppositely positioned with respect to one end of the cylinder. The displacer piston head serves as a heat exchanger for an object protruding into the cylinder from said opposite cylinder end. A member, having a cooling chamber, and a plurality of cooling fins is positioned behind the displacer piston head. Coolant can be delivered to and carried away from the cooling chamber by means of a hollow'displacer piston rod connected thereto. By this arrangement the displacer piston head heat exchangers is cooled.

CROSS REFERENCE TO RELATED APPLICATION This application is acontinuation-in-part of the priorfiled copending application Ser. No. 624,930, filed Mar. 21, 1967, now US. Patent No. 3,415,054, issued Dec. 10,

BACKGROUND OF THE INVENTION The present invention relates to an improved demonstration model of a'hot air motor and/ or heat pump for demonstrating to students the fundamental operating principles of such devices. The basic structural features of a demonstration hot air motor and/or heat pump, with which the present invention is concerned, is described in detailin detail in applicants priorfiled copending application, Ser. No. 624,930, filed Mar. 21, 1967 of which this application is a continuation-in-part. In particular, the invention relates to improvements in'demonstration models of a' hot air motor and/or heat pump which includes a transpa'rentcylinder, means for cooling at least a portion of the cylinder, a working piston slidablymounted within the cylinder, and a displacer piston slidably mounted within the cylinder between the working piston and one end of the cylinder. Both pistons are-connected to a common crank drive for displacement purposes. The displacer piston of such a model includes a displacer piston headhaving a central recess and a hollow displacer piston rod connected to such head. In addition, the. displacer piston head includes an inlet and anoutlet' for passage of heat exchange fluid therethrough. By this arrangement, the recess can receive a projection secured to the cylinder housing end opposite to the recess and the projection can enter into a heat exchange relationship with the contents of the cylinder. The projection maybe an element which is readily interchangeable, for example, an electrical heating element, a thermometer, or a specimen which is to be cooled or heated. Upon being received by the central recess of the displacer piston, favorable conditions of heat exchange are created.

3,481,142 Patented Dec. 2, 1969 ice It is the purpose of the present invention to improve the arrangement of parts just described by providing an effective cooling means for the displacer piston head heat exchanger.

It is therefore an object of the present invention to provide a relatively simple and improved displacer piston for the demonstration model.

While such a construction, as that described above, has proven to be a valuable tool, it has been found that the efficiency of the machine can be increased when the heat exchanger is modified, according to the present invention. In brief, the present invention contemplates that the displacer piston be provided with a cooling member having a cooling chamber through which coolant is circulated to remove heat from the displacer piston head heat exchanger.

By a further aspect of the invention, the cooling member is provided with a plurality of substantially radially extending cooling fins which are arranged in spaced-apart relationship circumferentially around the cooling chamber. Thus arranged, the cooling fins define heat exchange fluid passageways through which heat exchange fluid of the model passes after circulating through the inlet and outlet of the displacer piston head.

The cooling member, according to the invention, can be constructed in the form of a one-piece metallic plate. The displacer piston head can suitably be formed of hollow glass which is then glued onto or fastened in any other suitable manner to the metallic plate.

By yet a further aspect of the invention, the coolant is preferably supplied to the cooling chamber through which it circulates by means of a riser pipe concentrically mounted within a hollow displacer piston rod and in spaced-apart relationship to the inner wall thereof. Such an arrangement allows coolant to be supplied individually to the cooling chamber by way of the riser pipe. Moreover, coolant already in the cooling chamber can be drawn therefrom by way of a passage defined between the outer wall of the riser pipe and the inner wall of the hollow displacer piston rod. Thus constructed, it is possible to provide separate displacer piston rod inlet and outlet means outside the confines of the transparent model cylinder and near the lower end of the displacer piston rod. The inlet means can then be connected by way ofa flexible hose to a source of coolant supply while the outlet means can be connected by way of a flexible hose to a drain or sump.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 3 is a cross-sectional view along the line 22 of FIGURE 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGURE 1, a preferred embodiment of the present invention is schematically shown therein. A transparent cylinder 1 made from glassor plastic supports a displacer piston 2 and a working piston 3 which are slidably mounted with respect to one another within the cylinder 1. An object 18 is in position to have its heat exchanged.

According to the invention, the displacer piston 2 is provided with a displacer piston head 5 which includes a heat exchange fluid inlet 6 and outlet 7. Thus constructed, the displacer piston head 2 is able to serve as a heat exchanger within cylinder 1. The displacer piston head 5 is cooled by means of coolant which is circulated through a cooling member 4, which adjoins in back-up relationship the displacer piston 'head, by way of a hollow displacer piston rod 8. The displacer piston head 5, according to the invention, may be formed as a hollow body from a transparent material such as glass.

The displacer piston rod 8 is rigidly connected to the cooling member 4 which in turn adjoins the displacer piston head, as discussed above. The displacer piston rod passes through a central opening 9 in the working piston 3, the central opening 9 in the working piston 3 being sealed by a resilient gasket. The displacer piston rod 8 and working piston rod 10 are connected to a common drive means (not shown).

The interior of the diseplacer piston head 5 is hollow to permit the flow of heat exchange fluid therethrough by way of inlet 6 and outlet 7 preferably packed with porous material such as synthetic wool or copper wool. The displacer piston head 5 includes in its upper portion a central recess 11 for receiving an object projecting from cylinder 1 which is to have its heat exchanged, for example, a measuring instrument, a heating element or the like. The glass displacer piston head 5 is glued onto the cooling member 4.

Referring to FIGURES 2 and 3, the cooling member 4 is clearly shown therein. The cooling member 4 is in the form of a metallic plate-like cast piece and includes a centrally located cooling chamber 12 and a plurality of radially disposed cooling blades or fins 13. The cooling fins 13 are circumferentially arranged around the cooling chamber 12 in spaced-apart relationship to each other. Successive cooling fins 13 define together heat exchange fluid passageways 14. The cooling member 4 is so disposed with respect to piston head 5 that passageways 14 are at the vicinity of outlet 7. Heat exchange fluid passing through inlet 6, then to outlet 7 of the displacer piston head 5, in a substantially axial direction, will pass through the passageways 14 thus defined. The blades 13 and passageways 14 are best depicted in FIGURE 3.

Referring to FIGURE 2, the cooling chamber 12 is connected to the hollow displacer piston rod 8, as shown. The hollow displacer piston rod 8 includes a riser pipe 15 concentrically mounted within and spaced apart from the inside wall 16 of the piston rod 8. The riser pipe 15, as shown clearly in FIGURE 2, opens into the centrally located cooling chamber 12. The riser pipe 15 is connected to an inlet means 17 which is provided on a portion of the displacer piston rod 8 outside the cylinder. The inlet means 17 is connected in turn to a flexible hose 21 and then to a coolant source of supply (not shown).

The space formed between the riser pipe 15 and the inner wall 16 of the hollow displacer piston rod 8 defines an additional conduit 19 within the hollow piston rod 8. The conduit 19 serves as a return flow line whereby coolant having been circulated through the cooling chamber 12, as shown by arrows in FIGURE 2, is drawn therefrom to outlet means 20 and thereby to a drain or sump (not shown) provided therefor.

By the arrangement described above, the displacer piston head heat exchanger 5 can be effectively cooled 'by coolant which is introduced into the cooling member 4 by Way of the hollow diseplacer piston rod 8. The apparatus here described is a relatively simple means for facilitating efiicient operation of a hot air motor or pump demonstration model.

It will be understood that the above description of the present invention is susceptible to various modifications, changes, and adaptations.

I claim:

1. In a demonstration model of hot air motor and/or pump including a coolable transparent cylinder, a heat exchange fluid in said cylinder, a Working piston slidably disposed therein, a displacer piston likewise slidably disposed within said cylinder between one end of said cylinder and said working piston, said displacer piston having a displacer piston head oppositely positioned with respect to said one end of the cylinder, said displacer piston head being further defined by a central recess and an inlet and outlet which allows the flow of said heat exchange fluid therethrough, said displacer piston head thereby being a heat exchanger, an element for being received in said central recess, said element protruding from said one end of the cylinder said displacer piston head, whereby said element enters into a heat exchangerelationship with heat exchange fluid inside said displacer piston head and said displacer piston further having a hollow displacer piston rod connected to said displacer piston head whereby coolant is delivered to and carried away from said displacer piston head heat exchanger, the improvement wherein said displacer piston further comprises:

(a) a cooling irnember adjoining the back-up relationship said displacer piston head between said head and said hollow displacer piston rod;

(b) said cooling member having a cooling chamber provided therein; and

(c) said cooling chamber being connected to the hollow piston rod in such a manner as to provide delivery thereto and carrying away therefrom of said coolant.

2. The demonstration model defined in claim 1, said displacer piston cooling member further comprising a plurality of radially extending fiuid'passageways arranged around said cooling chamber and extending through said cooling member, whereby heat exchange fluid in said displacer piston head is allowed to flow past said cooling chamber.

3. The demonstration model defined in claim 2 wherein said cooling member is a plate-like element; said cooling chamber is centrally located therein; and said fluid flow passageways are further defined by a plurality of radially extending spaced-apart cooling fins circumferentially disposed around said cooling chamber, said fins being successively arranged to define said passageways between them.

4. The demonstration model defined in claim 3 wherein said plate-like element is formed of a metallic material.

5. The demonstration model defined in claim 3 wherein said hollow displacer piston rod is further defined by:

(a) a tube-like member concentrically mounted within and in spaced relationship to the inner wall of said piston rod;

(b) said tubelike member having an end which opens into said cooling chamber and another end connected to a fluid source inlet; and

(c) a conduit defined by the space between the inner Wall of said hollow rod and said tube-like member;

((1) said conduit being connected to an outlet drain whereby coolant introduced by said tube-like member into said cooling chamber and circulated therethrough exits therefrom by way of said conduit connected to said outlet drain.

6. The demonstration model defined in claim 1 wherein said displacer piston head is formed from a material having poor heat conducting characteristics.

7. The demonstration model defined in claim 2 wherein said displacer piston head has a hollow interior and is formed from glass.

8. In a demonstration model of a hot air motor and/or pump comprising a coolable transparent cylinder, a working piston slidably disposed Within said cylinder, a displacer piston slidably disposed withing said cylinder between an end of said cylinder and said Working piston, said displacer piston having a displacer piston head oppositely positioned with respect to said end of the cylinder and a central recess with an inlet and outlet for receiving an element to have its heat exchanged, and for allowing the flow of heat exchange fluid therethrough, an element which projects from said cylinder end into said central recess, the improvement wherein said displacer piston further comprises: a hollow displacer piston rod connected to said displacer piston head and including means whereby coolant for cooling said displacer piston head is delivered to and carried away therefrom.

References Cited UNITED STATES PATENTS 374,123 11/1887 Hopkins et a1. 6024 942,261 12/1909 Hubbard 6024 6 2/1963 Reinhart et a1. 6024 1/1964 Daniels et a1 6024 US. Cl. X.R. 

